1. Field of the Invention
The present invention relates to an image processing apparatus that captures tomographic images of an observation target, a control method of the image processing apparatus, and a program, and particularly, to a technique applicable to observation of tomograms of an eye portion.
2. Description of the Related Art
In recent years, an apparatus that obtains tomograms of a retina by Optical Coherence Tomography (hereinafter, called “OCT”) is implemented in clinical sites of ophthalmology, and new findings are provided. A plurality of tomograms of the retina can be obtained as volumetric images, and changes of each layer associated with the progression of disease can be quantitatively obtained across a wide range. This is expected to lead to highly accurate recognition of the degree of progression or evaluation of the treatment effect.
The relationship with the findings obtained by conventional methods is important to effectively utilize the images taken by the new apparatuses. For example, it is known that changes in the thickness of a nerve fiber layer are important in the diagnosis of glaucoma or in the evaluation of the treatment. Therefore, a C/D ratio (ratio of the cup and disc) obtained by fundus observation based on a slit lamp or a fundus picture is used as one of the effective indices.
Although three-dimensional information can be obtained by the observation based on the slit lamp, quantitative evaluation is difficult. On the other hand, although quantitative evaluation is possible in the fundus picture, three-dimensional information is lost. Therefore, Japanese Patent Laid-Open No. 11-151206 proposes a method related to acquisition and display of a shape of optic papilla using a stereoscopic fundus camera to obtain both the three-dimensional information and the quantitative evaluation. A method of approximately calculating the C/D ratio from the volumetric images obtained by the OCT is also proposed.
However, the information obtained by imaging by the stereoscopic fundus camera is just a combination of images obtained by capturing from different angles, and the information does not include tomographic information inside the retina. Therefore, there is a problem that the information inside the retina cannot be accurately obtained, as compared to the information of the volumetric images obtained by the OCT.
Furthermore, although detailed information can be obtained in relation to the nerve fiber layer, or the cup, in the OCT volumetric images, only approximate values can be obtained in relation to the sclera, or the disc. Therefore, in the conventional OCT volumetric images, it is difficult to present information that allows recognition of the entire image.